The Siemens 5SU1354-0LV20 is an FI/LS combination unit — an RCD (residual current device) and MCB (miniature circuit breaker) in a single 1+N-pole module. It is rated Type AC (WS), meaning it detects sinusoidal AC residual currents only, with a rated residual current IΔn of 30 mA and a short-circuit breaking capacity of 10 kA. The B 20 characteristic gives it a 20 A overcurrent trip curve for resistive and general-purpose loads, with the B-curve tripping between 3 and 5 times rated current for short-circuit protection.
What the Ratings Mean for Fit
The 30 mA IΔn is the standard sensitivity for personnel protection (shock hazard) in residential and commercial final circuits per IEC 60364. The 10 kA breaking capacity at the rated voltage covers most domestic and light commercial fault levels — verify the prospective short-circuit current at the installation point. The 1+N-pole format (switched phase, switched neutral) is common in single-phase TN-S and TT systems where the neutral must be disconnected for isolation. The D=70 mm width is a standard 4-module DIN-rail footprint, fitting a standard 4-MOD enclosure cutout.